Electroformed bipolar plates for fuel cells

Abstract

A bipolar plate assembly for a fuel cell is provided. The bipolar plate assembly includes a first electroformed unipolar plate disposed adjacent a second electroformed unipolar plate. The first and second unipolar plates are bonded by a plurality of localized electrically and thermally conductive plugs by electroplated material deposited within apertures formed in the substrates onto which the unipolar plates are electroformed. A method for forming the bipolar plate assembly is also described.

Description

FIELD OF THE INVENTION[0001]The present disclosure relates to fuel cell stacks and, more particularly, to a bipolar plate assembly and methods for preparing bipolar plates for fuel cell stacks.BACKGROUND OF THE INVENTION[0002]Fuel cells can be used as a power source in many applications. For example, fuel cells have been proposed for use in automobiles as a replacement for internal combustion engines. In proton exchange membrane (PEM) type fuel cells, a reactant such as hydrogen is supplied as a fuel to an anode of the fuel cell, and a reactant such as oxygen or air is supplied as an oxidant to the cathode of the fuel cell. The PEM fuel cell includes a membrane electrode assembly (MEA) having a proton transmissive, non-electrically conductive, proton exchange membrane. The proton exchange membrane has an anode catalyst on one face and a cathode catalyst on the opposite face. The MEA is often disposed between “anode” and “cathode” diffusion media or diffusion layers that are formed f...

AI Technical Summary

Benefits of technology

The patent describes a cost-effective and efficient bipolar plate assembly for fuel cells that has a strong structure and maximizes electrical contact between the plates while minimizing material usage and waste. The assembly includes two electroformed unipolar plates that are bonded together by multiple conductive plugs made of electroplated material. The method for preparing the assembly involves plating a substrate with a pattern and then placing two plated polymer sheets together, followed by applying a thickness of plating material to selectively bond the sheets together. This results in a highly effective and durable bipolar plate assembly for fuel cells.

Problems solved by technology

It is possible to achieve a desired minimal thickness of the substrate, but at a tradeoff to cost and to undesirable material properties.

For example, as a composite sheet is molded to a thinner dimension, it becomes more brittle and harder to work.

Additionally, a thinner composite sheet is often less desirable because high carbon content may cause a thinner sheet to become porous.

Similarly, as a metal sheet is thinned in multiple steps by drawing or rolling the sheet, it also becomes brittle or work hardened after each step, and requires annealing prior to further working.

Thus, a higher manufacturing cost is associated with a thinner substrate material.

A thinner metal substrate also limits the depth of any flow channel due to metal stretch limitations.

Additionally, conventional processes of forming the plates from the metal sheet material result in nearly half of the material being discarded as scrap.

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